1. Field of the Invention
This invention relates to a novel resin curable with an actinic energy ray and a method for the production thereof, more particularly relates to an actinic energy ray-curable resin which is soluble in an aqueous alkaline solution and capable of producing a film excelling in resistance to heat, electrical insulation properties, etc and a method for the production thereof.
This invention further relates to a photocurable and thermosetting resin composition which can be developed with an aqueous alkaline solution, contains the actinic energy ray-curable resin as mentioned above and hardens promptly by irradiation of an actinic energy ray such as an ultraviolet ray or an electron beam or further hardens by heating, more particularly relates to a photocurable and thermosetting resin composition which is excellent in storage stability, capable of producing a cured film excelling in resistance to heat, adhesiveness, electrical insulation properties, etc. without causing cracks, and adoptable in various application fields such as a solder resist to be used in the production of printed circuit boards, interlaminar insulating materials for build-up circuit boards, a plating resist, a photosensitive dry film, and fluorescent materials in the production of PDP.
2. Description of the Prior Art
In the soldering process which is carried out in mounting electronic parts on a printed circuit board, a solder resist is used for the purpose of preventing molten solder from adhering to irrelevant portions and protecting circuits. In recent years, a developing type solder resist composition which is used to form a pattern by a photolithographic method is widely adopted. Particularly, with due respect to the problem of environmental safety and from the viewpoint of cost, the solder resist composition of the alkali developing type has come to play the leading role. As a base resin used for these developing type solder resists, an actinic energy ray-curable resin obtained by the re-action of an epoxy resin with (meth)acrylic acid and the subsequent reaction of an acid anhydride with the resultant hydroxyl group of the modified resin is generally used.
Meanwhile, in consequence of the trend of IC and LSI parts toward highly dense mounting, the necessity of decreasing the width of circuit lines and the intervals between circuits of the printed circuit boards has been finding growing recognition. Besides, since the operating frequency of these parts to be mounted is enhanced, the heat value released from these parts increases accordingly. Therefore, the printed circuit board tends to require high thermal stability more than desired heretofore. In the actinic energy ray-curable resin obtained by using an epoxy resin as a starting raw material, however, since most of the functional groups which bond to an acid anhydride are secondary hydroxyl groups, the resin has the problem of relatively easily suffering the breakage of bonds when exposed to an increased temperature for a long time and, as result, inducing the possibility of degradation of such properties as insulation properties and resistance to heat and contamination of circuits due to the scattering of the decomposed acid anhydride.
In recent years, from the viewpoints of creation of a new organic reaction and its application to the synthesis of macromolecular compounds, the organic reaction involving the ring opening addition reaction of an oxetane ring which is an ether of four-membered ring has been studied. For example, the addition reaction of an oxetane compound and an active ester (T. Nishikubo and K. Sato, Chem. Lett., 697 (1992)) and the synthesis of polyester having a primary hydroxyl group attached to a side chain thereof by the polyaddition reaction of a bisoxetane and a dicarboxylic acid (T. Nishikubo, A. Kameyama, and A. Suzuki, Reactive.& Functional Polymers, 37, 19 (1998)) have been studied and reported. Further, the polyaddition reaction of a bisoxetane and a bisphenol has been reported recently (T. Nishikubo, A. Kameyama, M. Ito, T. Nakajima, and H. Miyazaki, Journal of Polymer Chemistry, Vol. 37, pp.2781–2790 (1998)) and tetraphenyl phosphonium bromide (TPPB) etc. are used as a reaction catalyst. However, these is no article which makes mention of the actinic energy ray-curable compositions of the present invention.
In general, a solder resist composition usually contains a polyfunctional epoxy compound having two or more epoxy groups as a thermosetting component for the purpose of improving the resistance to soldering heat.
Since the polyfunctional epoxy compound exhibits high reactivity, the photocurable and thermosetting resin composition containing this compound exhibits unduly short shelf life (useful life) and is liable to gain in viscosity prior to being applied to a blank circuit board. As a result, it is possible to formulate it as the one-package type only with difficulty. Accordingly, the composition requires to be formulated as the two-package type consisting of a hardener solution containing a polyfunctional epoxy compound as a main component thereof and a main agent solution containing a photosensitive prepolymer as a main component thereof and a curing promotor etc. added thereto. This poses the problem in working properties because it is necessary to mix them immediately prior to use.
Further, when the photocurable and thermosetting resin composition containing the polyfunctional epoxy compound is formed into a dry film, the shelf life (useful life) of this film becomes short and the preservation in the refrigerated state at a temperature of not more than 0° C. is required. That is to say, it is deficient in shelf stability at room temperature. Further, this dry film poses the problem in working properties because increase of its temperature to room temperature is required prior to use thereof.